The basic six pac intake has not changed at all. Aluminum or iron, cast in late '68 or 2004, they all have the same design. It's a decent part on the RB and with basically no mods but gasket matching it will make close to 600hp. The B wedge and 340 versions are more restrictive and I've seen 40hp drop going from a good dual plane and big 4bbl to a factory six pac setup on a 416" small block.
There were two other approaches - a short ram top for the cross ram base, and a medium-height tunnel ram witha replaceable top - both made by Edelbrock. A few years ago Indy made the Mod Man, which is basically a newer version of the Edelbrock low ram with replaceable tops. I haven't run the Mod Man, or the short ram. I have run the mid-rise Edelbrock and the factory ones. Personally I like the factory setup for 98% of applications. Once you get away from that, it gets to be more of a tuning nightmare for little improvement over a good single 4bbl intake.
